In an example of a known conventional damping valve for a shock absorber, an annular leaf valve is laminated onto an outlet end of a port provided in a piston portion of the shock absorber so that the port is opened and closed by the leaf valve.
In particular, with a damping valve in which an inner peripheral side of the leaf valve is supported fixedly and the port is opened and closed by causing an outer peripheral side to bend, a damping force generated when a piston speed is in a medium/high speed region may become excessive, thereby impairing passenger comfort in a vehicle. To solve this problem, JP09-291961A discloses a damping valve for a hydraulic shock absorber in which the inner peripheral side of the leaf valve is not supported fixedly, and instead, the inner periphery of the leaf valve is caused to slide against an outer periphery of a piston nut and a back surface of the leaf valve is biased by a coil spring via a main valve.
In the hydraulic shock absorber described in JP09-291961A, the leaf valve does not open when the piston speed is in a low speed region, and damping force is generated only by an orifice punched into a valve seat. As a result, a substantially similar damping characteristic to that of a damping valve having a fixedly supported inner peripheral side is exhibited. When the piston speed reaches a high speed region, on the other hand, the leaf valve bends so as to open and is lifted together with the main valve so as to retreat from the piston against a biasing force of the coil spring. As a result, a flow passage surface area increases in comparison with that of a damping valve having a fixedly supported inner peripheral side, thereby preventing the damping force from becoming excessive. The passenger comfort of the vehicle can thus be improved.